Compressor and vacuum pump



Dec. 6, 1932. c. PFEIFFER COMPRESSOR AND VACUUM PUMP `2 Sheets-Sheet 1 Filed April 15, 193C INVENTOR esar Pfeiffer B f mi a?" 1' ATTORNEYS Dec. 6, 1932. c. PFEIFFER coMPREssoR AND VACUUM PUMP Filed April l5, 193C 2 Sheets-Sheet 2` INVENTOR Cesar Pfeiffer B /ZML'NQ/ Ml/fn@ ATTORNEYS Patented Dec. 6, 1932 UNITED. STATES PATENT oFFlcE CSAR PFEIFFER, OF ASNIERES, FRANCE, ASSIGNOB TO FULLER COMPANYfA CORPORATION OF DELAWARE COMPRESSOR AND VACUUM Pour Application led April 15,

This invention relates to rotary comprising a stator casing having a substantially cylindrical bore in which a cylindrical rotor is arranged eccentrically, the rotor being provided with vanes to pocket the air or other gas. The invention is particularly directed to means for lubricating, sealing and simpliw fying the mechanical structure of the apparatus.

This invention is especially directed to an application of the invention described and claimed in the patent to Fradet, No. 1,543,155 of June 23, 1925. In the\apparatus of the 35 patent the forward edge of each vane, where it makes contact with the stator wall, is bevelled to an angle greater than the maximum angle formed by the normal to the vane and the tangent to the surface with which the vane contacts, for all positions of the vane, so that the lubricant is forced under pressure between the surfaces in contact. By this relation ofl parts, it has been possible to build compressors for operation at high pressures without requiring the usual vane retaining rings or interconnected vanes and to reduce the cost of construction and maintenance.V

This invention has particularly to do with a simple means for delivering the lubricant,

to distribute the latter uniformly within the slots of the rotor, on each side of the vanes, to form a uniform lm of-lubricant upon the stator wall and ultimately to remove a part of any excess lubricant or free water from the path of the vanes.. It isa further object of my invention to form the stator wall so that by distributing the lubricant as described above, an effective seal is provided to permit high pressure operation or high vacuum without loss of efficiency.

For simplicity, my invention shall be described and claimed as an air compressor, but it is to be understood that it can be used to compress other gases and as a vacuum pump.

In general the apparatus comprises the following major element-s.- Each stator casing is provided with a central bore having an air inlet on one side and an outlet for compressed air on the opposite side. The bore is cylin- .0 drical except for a small segment between 1930. Serial No. 444,447.

the air inlet and the air outlet. This segment, although cylindrical, is of shorter radius than the larger portion of the bore. Its center is on a radius of the larger portion, but displaced outwardly so that this portion of the wall of the bore is slightly beyond the wall of the larger cylinder. The function of this segment is to cooperate with the rotor and vanes to form a pressure seal, to be described later. The solid cylindrical rotor, o provided with integral stub shafts mounted in radial bearings in cylinder heads at each end of the casing, is arranged parallel but eccentrically to the center line of the larger cylinder. The rotor and the seal portion of the inner wall of the casing are concentric and are cleared to a minimum of a running fit, corrected for working temperatures.

The rotor is provided with a plurality of substantially radial slots in which thin vanes are arranged to slide freely and to move out: wardly by centrifugal force into contact with the inner walls of the casing. The incoming air is trapped in cells formed by the walls of the cylinder, rotor and the vanes, the contents of these cells decreasing progressively dur lng rotation to increase the pressure of the a1r.

The lubricant is delivered under pressure to each cylinder head, through which it passes through a duct and discharges into one end of a curved groove formed contra to the direction of rotation in the inner surface of the cylinder head on the air inlet side. This groove preferably conforms substantially tov the curve described by the bases of the vanes in their outward positions during rotation, so that as the pressure under which the lubricant is delivered is greater than the compressor pressure throughout the length of the groove, the lubricant is drawn or sucked into the slots. The outward movement of the vanes also tends to pump lubricant into the slots and as the vanes are forced inwardly the 95 oil passes outwardly on `either side of the vanes due to this displacement and centrifugal force. This even distribution insures .the formation of a thin film of lubricant to provide a running surface for the edges of the vanes on the inner wall of the stator casing.

The inner wall of the casing is provided with a groove near the air outlet in order to 5 catch and discharge free water and excess lubricant into the air outlet and to form a reservoir for a small quantity of lubricant to aid in its uniform distribution. As the vanes pass the air discharge outlet they contact with the seal portion of the wall, at least two and preferabl three of the vanes being kept in contact to orm the seal to prevent loss of pressure. That is, the arc of the cylindrical segment or seal portion of the casing wall is 5 greater than the arc determined by two ado.. the usual loss in volumetric efliciency I have also been able to build vacuum pumps in accordance with the invention which have p produced a higher vacuum than any mechanlcal vacuum pump of which I am aware.

For a better understanding of the invention, reference will be made to the accom- R Fig. 4 is a detail of a der wall on line 4-4 of panying drawings, in which:

Fig. 1 is a partial longitudinal section of the apparatus;

Fig. 2 is a cross section in an enlarged scale of one stage on line 2 2 of Fig. 1;

Fig. 3 1s a view of the inner face of one cylinder head in elevation,

portion of the cylin- Fig. 2, in the direc tion of the arrows. Referrin now to the drawings, and first to Fig. 1, t e apparatus is shown to consist of a low pressure stage 10, a high pressure stage 11 rigidly mounted upon the upper surface of b ase 12. For the sake of clearness in illustration, only half of the low pressure stage is shown, as the remainder of the apparatus is exactly similar as will also be aparent from the high preure stage 11. The

ow pressure stage 10, and thehigh pressure stage 11 are identical in design, exce t for size, the hi h pressure stage being sma er as it receives t e air from the low pressure stage. Each stage comprises a stator casing 13, having an air inlet 14 and an air outletil, opening into a substantially cylindrical central bore 16 (Fig. 2). The arger portion of the circumference of this bore between the ar' rows 17 and 18 is cylindrical in form with the center at 19. The smaller section of the bore between the arrows 17 and 18 is a segment of a cylinder of shorter radius than the larger portion and its center 20 is displaced from the center 19, the centers 18 and 20 preferably being ,on a common vertical center line.

The cylindrical rotor 21 isarranged eccentrically within the bore 16, but on the center 20, the wall of the rotor clearing the smaller cylindrical se ment the minimum distance of a running tigt corrected for temperature. That is, the actual clearance must be increased as the diameter of the rotor is in- `creased to compensate for expansion of the rotor. -As the smaller cylindrical segment and the wall of the rotor are concentric for the distance between the arrows 17 and 18, indicated in Fig. 2, a pressure seal is formed as'will be described later.

Each rotor 21 is provided with substantially radial slots 22 in which thin vanes 23 are arranged to slide freely and move outwardly into contact with the walls of the bore 16 during rotation. The contacting edges of the vanes are preferably bevelled, as described in the Fradet patent above noted. 'Each rotor 21 is provided with integral stub shafts 24 and 25 mounted in rigid radial bearings 26 and 27 29 which close opposite ends of the bore of the stator casing 13.'

The lubricant, preferably'a light engine oil, is supplied to the apparatus in the following manner. A force feed lubricator pump 30, of any type capable of supplying oil under the proper operating pressure, is conveniently mounted on a bracket 31 secured to the cylinder head 28. This pump may be driven by"connecting its drive shaft 32 to the rotor stub shaft 25. The lubricator 30 delivers thexoil through tubes 33 to sight feed lubricators 34 mounted in the cylinder heads and -which discharge into ducts 35. bored radially in the heads These ducts are and open as at 36 into the bore of the stator casing 13. 'Each duct 35, and its discharge o enin 36 terminates in one end of a groove 37. .Tis groove extends towardthe inlet side of the casing, as indicated in Fig. 3, and is curved to conform substantially to the curve 'defined by the bases of the vanes in their outward positions in the slots during rotation as they pass the corres onding arc of the bore. The groove 37 lies etween the .base of the vanes 23 and the bottom of the slots 22, so that the oil has a free admission to the slots.

As indicated, in Fig. 3, the groove 37 extends contra to the direction of rotation, as indicated by the arrow. This ligure i1lus trates one of the heads 28, andit should be noted that the grooves cut in the heads 29 run in the opposite direction, so that all grooves 37 extend toward air inletsgll when the heads are secured to the casing 13.

in cylinder heads 28 and l aid in the distribution well as any excess of oil into the discharge f opening and to prevent the entrance ot water and excess oil into the seal space formed by the rotor 21 and the smaller cylindrical segment of the bore.-

The operation of the apparatus is as lows and is reerred to one stage as two or more stages operate similarly. The air is drawninto the casing ot' the low pressure stage through lan intake regulator not shown, through the inlet opening 14, and into the bore 16 where it is trapped in cells formed by the vanes and the walls of the bore 16 and the rotor 21.. The cells decrease in volume and deliver the air through the outlet 15. Passing the outlet 15 the vanes are forced into their innermost position in passing the cylindrical segment between the arrows 17 and 18 where they cooperate with the walls of the rotor and the segment to orm a seal against loss of pressure between the outlet 15 and the inlet 14', this seal being maintained by the lubricant which covers all surfaces, as will be described later.

The oil' or other lubricant delivered trom y the pump to the sight feed lubricators 34 is regulated in proper quantity and admitted to the ducts under pressure. As these ducts open into the bore inL the region ot minimum compressor pressure, and as the oil is delivered under higher pressure most o the oil is drawn or sucked into the rotor slots 22 near their bases as they travel past the groove however., is distributed between the inner sur.-

. tace of the cylinder heads, such as 28 and 29 and the ends of the rotor 21 which forms an eective seal for each end of the casing. The outward motion of the vanes 23 causes a slight decrease in pressure in the slots which also tends to draw oil into the slots. The oil distributes uniformly over the vanes due to centriugal force and the displacement by the vanes as they are forced inwardly during rotation by the wall of the bore. The bore of the casing is thus provided with a uniformly distributed iilm of lubricant as particularly described in the patent to Fradet above identified. Any excess of oil or free water which may occur due to condensation when the compressor i idle or otherwise is trapped in the grooves 38 and 39 and ultimately discharged into the outlet 15. These grooves also act as a reservoir to o oil. As the varies are rotated rapidly, the in- 37. A small quantity of the oil,

ertia ot the oil tends to hold it stationary on all wall surfaces and it is thus subjectedto a pressure which forces it between the contacting surfaces of the inner walls of the bore and the bevelled edges of the vanes 23. This is also true of the cylindrical segment, and due to its relation of parts and the oil film, an eiiective seal is provid-ed against loss of pressure between the outlet and the inlet.

By this system of lubrication and sealing against loss otpressure, I not only reduce y wear to a minimum, but am enabled to couple two or more stages directly bymeans of a coupling such as that shown at l0 without damaging the working parts of either stage.

l claim:

1. A rotary compressor comprising a stator casing having a central bore, an air inlet on one side ofthe casing and an airputlet on the opposite side, a cylindrical rotor pro vided with substantially radial slots, vanes movable within the slots, the rotor being arranged eccentrically within the bore between heads at each end of the casing, at least one of the heads being provided with a duct and an oil groove 'for the How of lubricant opening into the bore between the base of a vane and the bottom of the corresponding slot and near the inlet side ot the casing, said groove extending from said bore in a direction opposite to the direction of rotation of the rotor.

2. A rotary compressor comprising a stator casing having a central bore, an air inlet on one side of the casing and an air outlet on the opposite side, a cylindrical rotor provided with substantially radial slots, vanes movable within the slots, the rotor being arranged eccentrically within the bore between heads at each end of the casing, at least one et the heads being provided with a duct and a groove on its inner face into which the duct opens, said groove extending toward the air inlet in a direction opposite to the direction oi rotation of the rotor and opening into the bore between the bases of the vanes and the bottom of the slots and means for supplying a lubricant under pressure to the duct.

3. A rotary compressor comprising a stator casing having a central bore, an air inlet on. one side ot the casing and an air outlet on the opposite side, a cylindrical rotor provided with substantially radial slots, vanes movable within the slots. the rotor being arranged eccentrically within the bore between heads at each end of the casing at least one ot the heads being provided with a duct and a groove on its inner face into which the duct opens, the groove extending toward the air inlet of the casing in a direction opposite to the direction of rotation of the rotor, and means for supplying lubricant to the duct.

4. A rotary compressor comprising a stator casing having a centra-1 bore, an air inlet on one side ot the casing and an air outlet on the opposite side, a cylindrical rotor provided forced outwardly during vided with substantially radial slots, vanes movable within the slots, the rotor beingarranged eccentrically within the bore between heads at each end of the casing, at least one of the heads being provided with a duct and a groove on its inner face into which the duct opens, the groove being curved and extending in a direction opposite to the direction of rotation of the rotor and toward the air inlet side of the casing, and opening into the bore between the bases of the vanes and bottom of the slots and means for supplying lubricant to the duct. n

5. A rotary compressor comprising a stator casing having a central bore, an air inlet on one side of the casing and an air outlet on the opposite side, a cylindrical rotor provided with substantially radial slots, vanes movable within the slots, the rotor being arranged eccentrically within the bore between heads at each end of the casing, means for supplying a lubricant to the slotswhich will be rotation of the rotor to form a film on the inner wall of the casing, the inner wall of the casing being provided with a groove beginning at a level slightly above and inclined downwardly and opening into the air outlet of the casing for discharging excess lubricant intothe air outlet of the casing.

6. A rotary compressor comprising a stator casing having a central bore, an air inlet on one side of the casing and an air outlet on the opposite side, a cylindrical rotor provided with substantially radial slots, vanes movable within the slots, the rotor being arranged eccentrically within the bore and mounted on heads. at each end of the casing, means for supplying a lubricant to the slot-s which will be forced outwardly during rotation of the rotor to form a film on the inner wall of the casing, the inner wall of the casing being proslightly above and inclined downwardly and opening into the air outlet of the casing to discharge excess lubricant into the air outlet of the casing. 1

In testimony whereof I alix my signature.

CSAR PFEIFFER.

with grooves beginning -at a level 

